1. Field of the Invention
The invention is directed to a method for reducing the nitric oxide concentration in the waste gas flow of combustion processes in which a treatment medium is introduced into the waste gas flow and the waste gas flow is subjected to an additional compulsorily produced turbulence as well as to a compression and subsequent relaxation and calming. The invention is also directed to an apparatus for implementing the method.
2. Background Art
In order to reduce the nitric oxide concentration in the waste gas flow of combustion processes it is known to introduce various chemicals, e.g. ammonia, sal ammoniac, urea, calcium cyanamide, into the waste gas flow of a combustion system. The chief consideration in all these methods was previously given to the feed of chemicals in determined temperature ranges. In order to arrive at usable results the chemicals were introduced at a plurality of locations, wherein the composition and concentration of the chemical solutions or chemical suspensions were adapted to the temperature conditions prevailing in the different feed planes. In order to achieve a good distribution of the introduced chemicals, a large quantity of feed locations and feed nozzles had to be provided. These steps are not only costly with respect to construction, but also require a large expenditure on regulating technology.
In the method mentioned in the beginning, which is known from DE 36 10 669 A1, in order to improve the above-mentioned conditions, a rotational flow having a certain inner turbulence is first brought about in an inlet chamber, which is circular in cross section, by means of tangential admission of flue gases. A Venturi device is connected to this chamber, the flue gases being compressed and accelerated vertically upward in the confusor of the Venturi device. The treatment medium is introduced at the location of highest acceleration and compression which is formed by the throat of the Venturi device, whereupon the mixture is relaxed in the subsequent diffusor and is then directed into an ascending pipe shaft in which the actual reaction occurs. As a result of the compression and upward acceleration, the spiral flow is pulled apart, which leads to a uniform flow, so that the certain production of turbulence is no longer effective to the desired extent prior to the introduction of the medium. The compression zone is very short, so that no reaction occurs here which first takes place in the homogenized and calmed flow. This known treatment method takes place in an apparatus which is independent of the furnace, so that an additional construction expenditure is required specifically for the treatment of the flue gas.